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Your third trimester

Weeks 28–40+ (28 weeks 0 days until birth)

The third trimester starts at 28 weeks 0 days and lasts until your baby is born. The brain grows rapidly, the lungs mature and the fetus adds body fat, and it typically turns head-down before birth. Appointments become more frequent, and you should keep feeling your baby move right up to and during labor.

Gouache illustration of a ripe apricot on a leafy branch
First0 to 13+6
Second14+0 to 27+6
Third28+0 to birth
Weeks of pregnancy counted from the first day of the last period, using ACOG trimester boundaries. The apricot band marks early, full and late term (37+0 to 41+6).

How your baby develops

  • The brain grows rapidly during the third trimester, and the nervous system begins to control some body functions.1,2
  • Between about 27 and 30 weeks, the eyelids can open and close.1,2
  • The lungs begin to make surfactant. Rhythmic breathing movements start around weeks 31 to 34, although the lungs are not yet fully mature, and they are close to fully developed by the ninth month.1,2
  • The fetus gains a lot of fat in these weeks, which helps after birth. By about 35 to 37 weeks, fat under the skin makes it look less wrinkled.1,2
  • The major organs keep developing so that they are fully working by birth. By the last weeks, most of the lanugo hair has gone, apart from small patches on the upper arms and shoulders.1,3
  • The fetus typically moves into a head-down position during the third trimester, which is the best position for birth.3

Changes you may notice

  • Everyone experiences the third trimester differently. Common symptoms include Braxton Hicks (practice) contractions, shortness of breath, heartburn and needing to pee more often.3
  • Swelling, varicose veins, hemorrhoids and trouble sleeping are also common. Swelling that comes on suddenly in your face, hands or feet is different and needs to be checked straight away, as it can be a sign of pre-eclampsia.3,4
  • Some people feel an urge to get ready for the baby, often called nesting. It is also fine if you never feel it.3
  • You should feel your baby move right up to and during labor. If movements slow down, stop or change from the usual pattern, call your provider or maternity unit immediately, even in the middle of the night. Do not use a home Doppler to check the heartbeat yourself.5

Care in this trimester

  • In the US, prenatal visits are usually every two weeks until 36 weeks and then weekly, or more often for a high-risk pregnancy. In the UK, appointments are typically offered at 28, 31 (first pregnancy), 34, 36, 38, 40 and 41 weeks.3,6
  • If you are Rh D–negative and have not developed antibodies, Rh immune globulin is usually offered at around 28 weeks.7
  • In the US, Tdap is recommended during weeks 27 through 36, preferably early in that window. The maternal RSV vaccine (Abrysvo) is given at 32 to 36 weeks, from September to January in most of the US. In the UK, the RSV vaccine is offered from 28 weeks, ideally as soon as possible after that.8,9,10
  • In the US, screening for group B strep is done between 36 weeks 0 days and 37 weeks 6 days.11
  • Near the end of pregnancy, some providers check your cervix, and a nonstress test or biophysical profile may be recommended for high-risk pregnancies or those that go past the due date.3
  • Your care team will typically talk about the signs of labor and when to call. Calling is advised if you think you are in labor, have regular contractions every 5 minutes or more often, or your water breaks, and urgently if you are less than 37 weeks pregnant and think you might be in labor.12

Questions to ask your provider

  • Which vaccines do you recommend for me in the third trimester, and when?
  • When should I call you or go in if I think labor has started?
  • Is my baby head-down, and what happens if not?
  • Will I have a group B strep test, and what does the result mean for labor?
  • What happens if I go past my due date?

Week by week

When to contact your provider straight away

Call 911 (US) or 999 (UK) in an emergency, such as heavy bleeding or bleeding with severe pain, a seizure, chest pain, or severe trouble breathing.4,15,16,17

These symptoms are not always serious, but each one needs prompt advice from your provider, midwife or maternity unit (or NHS 111 in the UK if you cannot reach them) rather than waiting for your next appointment, and it helps to tell them you are pregnant.

  • Vaginal bleeding or spotting at any stage of pregnancy. Call 911 or 999 if the bleeding is heavy or comes with severe belly pain, shoulder pain, or feeling faint or dizzy.16,18
  • Fluid leaking or gushing from your vagina, or discharge that is unusual for you. Get checked straight away if the fluid is greenish, colored or smells bad.12,16,17,19
  • Your baby moving less than usual, not moving, or a change in their usual pattern of movements. Call immediately, even in the middle of the night, and do not use a home Doppler to check yourself.5,16
  • A severe headache that does not go away with simple painkillers or gets worse, or sudden changes in your vision such as blurring or seeing flashing lights.4,16,17
  • Sudden swelling of your face, hands or feet, or swelling, redness or pain in a leg.4,16,17
  • Belly pain that is severe or does not go away after resting, or pain just below the ribs.4,16,20
  • Regular tightenings or contractions, period-type pains, or backache that is unusual for you before 37 weeks, which can be signs of preterm labor.19,20
  • A fever of 100.4°F (38°C) or higher, or feeling hot, cold or shivery.16,17,19
  • Shortness of breath that comes on suddenly or happens when you lie flat, chest pain, a racing or pounding heart, or dizziness or fainting.16,17
  • Very itchy skin, especially on the palms of your hands or soles of your feet, or itching that is worse at night.21
  • Being sick so often that you cannot keep food or drink down, or signs of dehydration such as dark urine, peeing very little, or feeling dizzy.16,22
  • Thoughts of harming yourself or your baby. Get help right away, and call 911 or 999 if you think you might act on them.16,23

Questions about the third trimester

When does the third trimester start?

The third trimester starts at 28 weeks 0 days and lasts until birth. Some sources start it a week later, but most providers count 28 weeks as the start.3,13

What does full term mean?

Early term is 37 weeks 0 days to 38 weeks 6 days, full term is 39 weeks 0 days to 40 weeks 6 days, late term is 41 weeks 0 days to 41 weeks 6 days, and postterm is 42 weeks 0 days onward.14

How often are appointments in the third trimester?

In the US, visits are usually every two weeks until 36 weeks, then weekly. In the UK, appointments are typically at 28, 31 (first pregnancy), 34, 36, 38, 40 and 41 weeks.3,6

Do babies move less near the end of pregnancy?

You should feel your baby move right up to and during labor. If movements slow down, stop or change, call your midwife, provider or maternity unit immediately rather than waiting.5

Sources

  1. Fetal developmentUS National Library of Medicine
  2. Fetal Development: Week-by-Week Stages of PregnancyCleveland Clinic
  3. Third Trimester of Pregnancy: Overview & When It StartsCleveland Clinic
  4. Pre-eclampsiaNHS (England)
  5. Your baby's movementsNHS (England)
  6. Your antenatal appointmentsNHS (England)
  7. Practice Bulletin No. 181: Prevention of Rh D AlloimmunizationAmerican College of Obstetricians and Gynecologists, 2017
  8. Tdap Vaccination for Pregnant WomenUS Centers for Disease Control and Prevention
  9. Protecting Infants from RSVUS Centers for Disease Control and Prevention
  10. Vaccinations in pregnancyNHS (England)
  11. Committee Opinion No. 797: Prevention of Group B Streptococcal Early-Onset Disease in NewbornsAmerican College of Obstetricians and Gynecologists, 2020
  12. Signs of going into labourNHS Best Start in Life
  13. How Your Fetus Grows During PregnancyAmerican College of Obstetricians and Gynecologists
  14. Committee Opinion No. 579: Definition of Term PregnancyAmerican College of Obstetricians and Gynecologists, 2013
  15. Epilepsy and pregnancyNHS (England)
  16. Urgent Maternal Warning Signs and Symptoms (Hear Her campaign)US Centers for Disease Control and Prevention
  17. Pregnancy symptoms you need to get help forNHS (England)
  18. Vaginal bleeding in pregnancyNHS (England)
  19. Premature labour and birthNHS (England)
  20. Stomach pain in pregnancyNHS (England)
  21. Itching in pregnancyNHS (England)
  22. Severe vomiting in pregnancyNHS (England)
  23. Depression in pregnancyNHS (England)

Links checked November 12, 2026. Citing a source does not mean it endorses this site.